New dimensions of minting

The Mint of Poland produces a coin in the shape of a sphere. An upstroke hobbing press by Sack & Kieselbach is being used for this.

The small Pacific island state of Niue is known among numismatists as publisher of unusual coin creations. The current “coin” is shaped like a sphere and shows a historical map indicating the seven new wonders of the world with crystals.

The renowned Mint of Poland undertook the realisation of this demanding project.

A technical challenge

Thanks to modern software like ArtCAM, the spherical projection of the design and the following laser engraving are not a big problem nowadays. However, imprinting the entire surface of a round body and designing suitable tools required the development of completely new and innovative solutions. It took the experienced experts of the Mint of Poland several approaches to solutions and numerous practical trials to achieve the perfect final result.

Image 2: Initial minting trials without design made of copper.

Image 3: Blank made of rough-turned silver. The sphere was made with excess material. The trick was to precisely dimension this material reserve.

Image 4: The completed tool consisting of four segments and a pair of coining dies

Image 4: Tool with inserted blank

„We used a press by Sack & Kiesselbach for this Project, because we wanted to have the greatest control possible over all Parameters of the minting process.“

Siemowit Kalukiewicz, Mint of Poland

Image 5: The final product was shown on the WORLD MONEY FAIR 2015 and is now on the market.

Engineering and skilled precision work bring the desired result

The perfect result is made possible through the precise interaction of tool and press. The spherical coin is produced on an upstroke hobbing press by Sack & Kieselbach via manual feeding operation. The advantages:

Precise control of the press stroke.

The hydraulic press works power-controlled, displacement-controlled and time-controlled and makes control of the entire minting process in the hundredth millimetre range possible.